Acetylferrocene modified carbon paste electrode; A sensor for electrocatalytic determination of hydrazine

The electrocatalytic oxidation of hydrazine at a carbon paste electrode spiked with acetylferrocene as a mediator was studied by cyclic voltammetry, differential pulse voltammetry, and chronoamperometry. In contrast to other ferrocenic compounds, acetylferrocene exhibits a chemical irreversible behavior, but it can act as an effective mediator for electrocatalytic oxidation of hydrazine, too. The heterogeneous electron transfer rate constant between acetylferrocene and the electrode substrate (carbon paste) and the diffusion coefficient of spiked acetylferrocene in silicon oil were estimated to be about 3.45 x 10(-4) CM s(-1) and 4.45 x 10(-9) cm(2) s(-1), respectively. It has been found that under the optimum conditions (pH 7.5) the oxidation of hydrazine occurs at a potential of about 228 mV less positive than that of an unmodified carbon paste electrode. The catalytic oxidation peak current of hydrazine was linearly dependent on its concentration and the obtained linear range was 3.09 x 10(-5) M - 1.03 X 10(-3) M. The detection limit (2 sigma) has been determined as 2.7 x 10(-5) M by cyclic voltammetry. Also, the peak current was increased linearly with the concentration of hydrazine in the range of 1 X 10(-5) M - 1 X 10(-3) M by differential pulse voltammetry with a detection limit of I X 10-5 M. This catalytic oxidation of hydrazine has been applied as a selective, simple, and precise new method for the determination of hydrazine in water samples.